Thermo-torque motor



4June 6, 1967 R. w, Buss 3,323,460

THERMO -TORQUE MOTOR Filed 001,. 26, 1964 INVENTOR l ROBERT WAYNE Buss lBY WM @Wk/f' y/olgus United States Patent O 3,323,460 THERMO-"ICORQUIElMTOR Robert Wayne Bliss, Champaign, Ill., assignor to The MagnavoxCompany, Fort Wayne, Ind., a corporation of Delaware Filed Oct. 26,1964, Ser. No. 406,370

2 Claims. (Cl. 102-76) This invention relates generally to actuators ormotors used in devices where one-time yoperation is required, and moreparticularly to a motor which utilizes a chemical combustion directlyfor imparting a rotary motion to an output member.

Known types of explosive actuated drive devices such as dimple motors,bellows motors, and piston motors, are used to provide some type oflinear output motion or force from which rotary motion or torque can beachieved by mechanical linkages. However, in view of the nature of thework to be performed by such devices and in view of the simplicity ofthe present invention, such prior art devices are rather complex. Thisresults in an excessive space requirement and necessitates theincorporation of more parts than is 'desired for assuring reliabality.

It is therefore a general object of the present invention to provide adevice which can yield a rotary motion or torque directly from anexothermic chemical reaction without the necessity of means forconverting linear to rotary motion.

A further object is to provide a device achieving this result withmaximum reliability in minimal space and using materials which arereadily available.

Described briefly, a typical embodiment of the present inventionincludes a case having a chamber therein and a rotor having a shaftextending through a wall of the case and mounted for rotation in thecase. The chamber has a pyrotechnic compound therein with some type ofigniter communicating therewith so as to enable ignition of the compoundby the application of some external initiator thereto such as, forexample, an electrical voltage.

A bimetal spiral is embedded in the pyrotechnic compound and has itsouter end affixed to the case. The inner end of the spiral is connectedto the rotor shaft. Application of a voltage to the igniter initiatescombustion in the pyrotechnic compound whereupon the heat generatedcauses the spiral to unwind, rotating the rotor. In a typical example,this rotation is used to align an explosive charge mounted in the rotorwith an explosive charge and detonator means in an arming device.

The full nature of the invention will be understood from theaccompanying drawing and the following description and claims.

FIG. 1 is a longitudinal section through an arming device constructedaccording to a typical embodiment of the present invention.

FIG. 2 is a cross section taken on the line 2-2 in FIG. 1, and viewed inthe direction of the arrows.

Referring now to the drawings in detail, the illustrated arming deviceincludes a cylindrical housing 11 with a block 12 in one end thereofhaving a booster charge 13 disposed in an aperture therein. A block 14is disposed in the housing and doweled by the pin 16 to the block 12. Acavity 17 is formed between the block 12 and the block 14 for receivinga disc portion 18 of a rotor 19 mounted in a bearing block 21 forrotation therein on the axis 22.

A 'block 23 having a chamber 27 is also secured in the housing 11. A pin24 or other suitable means can be used to join the block 23 to the block21 and to the block 14, to prevent relative rotation between the blocks23, 21, 14 and 12. A bimetal coil which is illustrated in the form of aat spiral 26, but which could have other configurations, is received inthe chamber 27 in the block 23. The spiral 26 has its outer end 28received in an axially extending groove in the block 23 and aflixedthereto. The inner end 29 of the spiral 26 is received in an axiallyextending groove 30 in the rotor 19 and is aiiixed thereto. In theillustrated example, the means aixing the ends 28, 29 of the spiral 26to the block 23 and the rotor 19 happens to be a force tit. Other meanscould also be employed if desired.

The spiral 26 has a bimetal construction with two layers 31, 32. Thefirst or inner layer 31 is made of a metal that has a higher rate ofthermal expansion than does the metal of the second or outer layer 31,32 joined thereto. These layers make up a unit which, when subjected toincreases of temperature, tends to straighten out. The spiral 26 isembedded in a rapid burning or pyrotechnic compound 33 in the chamber 27and, when this compound 33 is ignited -by a suitable igniter 34 andburned, the heat transmitted to the spiral 26 rotates the rotor 19. Thespiral 26 should provide this rotation prior to being melted or withoutbeing melted by the heat of the ignited compound 33. The igniter 34 maybe chemical, electrical or mechanical in nature, the electrical typebeing illustrated with two leads 36 and 37.

In the arming device the rotor 19 is normally disposed with an explosivecharge 38 disposed 180 out of line with the booster charge 13 and adetonator 39.The detonator 39 can be electrical, chemical or mechanical,in nature. The detonator 39 and the explosive charge 38 are spaced thesame radial distance from the axis 22 on a straight line passing throughthe axis 22. A hole 41 is provided in the rotor 19 and is normallydisposed 180 away from a detent pin 42 in the block 14, this pin 42being spring loaded by the coil spring 43. When the igniter 34 isinitiated -or set oil to ignite the compound 33, the spiral 26 isheated, rotating the rotor 19. When the rotor 19 rotates 180, the detentpin 42 can be received in the hole or aperture 41 in the rotor 19 tothereafter retain or lock the rotor 19 in an armed condition with thedetonator 39, the explosive charge 38, and the booster charge 13aligned. Therefore, even if the spiral 26 cools, it can not rewind orturn the rotor 19 to the unarmed position.

Of course there may tbe instances in which the novel motor of thepresent invention is desired to return the rotor to its originalposition or some position intermediate the original position and thearmed position after cooling, and this can be accomplished.

In the illustrated example, the arming device has the 180 out-of-linesafety features and yet can be armed as desired upon receipt of anarming signal at the igniter 34, utilizing essentially no mechanicallinkage and providing reliable operation. When the device is armed, thedesired explosive output can be obtained by providing a firing signal tothe detonator 39. Other angles of position and rotation, for example maybe used in place of the 180 position and rotation described.

Using readily available materials, the rotation of the rotor uponapplication of energy to the igniter occurs so quickly that it cannot befollowed by the human eye. Among the advantages of the present inventionare: low cost, long shelf life, freedom from maintenance, compact,lightweight, safe to handle, reliability, simplicity, adaptability toelectrical or mechanical initiation, rugged construction, versatility ofform factor, capability for high amplification or attenuation, tolerancefor very small or very high input signals.

While the invention has been disclosed and described in some detail inthe drawings and foregonig description, they are to fbe considered asillustrative and not restrictive in character, as other modificationsmay readily suggest themselves to persons skilled in this art and withinthe broad scope of the invention, reference being had to the appendedclaims.

I claim: 1. An arming device comprising: a housing;

a rotor mounted for rotation in said housing, said rotor having anelongated shaft and having a rotor disc on said shaft, said disc havingan axially extending aperture therethrough disposed at a predeterminedradius from the rotor rotational axis, said aperture having a firstexplosive charge therein;

an electrical detonator aixed in said housing;

an explosive booster charge disposed in said housing, said rotor discbeing normally disposed in a space between said detonator and saidbooster charge and isolating said detonator from said booster chargewhen said rotor is in an unarmed position, said rst explosive chargebeing in a position remote from said detonator and charge when saidrotor is in said unarmed position;

an electrical igniter disposed in said housing and communicating With amotor chamber therein;

a pyrotechnic compound disposed in said chamber and ignitable -by saidigniter;

a bimetal spiral disposed in said chamber and embedded in saidpyrotechnic compound, the outer end of said spiral being affixed to saidhousing and the inner end of said spiral being aflixed to said rotor,said spiral being responsive to combustion of said pyrotechnic compoundto rotate said rotor shaft and thereby said rotor from said unarmedposition to an armed position wherein said rst explosive charge isaligned with and in communication with said detonator and said explosivebooster charge;

and first detent means in said housing and second detent means in saidrotor, said rst and second detent means being aligned and operable Whensaid rotor is in said armed position to maintain said rotor in saidarmed position.

2. An arming device comprising:

a housing;

a rotor mounted for rotation in said housing, said rotor having anelongated shaft and having a rotor disc on i said shaft, said dischaving an axially extending aperture therethrough disposed at apredetermined radial distance from the rotational axis of said rotor;

a detonator lmounted on said housing on one side of said rotor disc;

an explosive booster charge mounted on said housing on the opposite sideof said rotor disc;

said detonator and said booster charge being positioned along an axisthat is parallel to said rotational axis and spaced from said rotationalaxis by said radial distance so that said rotor disc isolates saiddetonator and said booster charge with said rotor aperture spaced fromsaid -detonator and said booster charge in an unarmed position of saidrotor;

motor chamber positioned in said housing around said rotor shaft;

a bimetallic spiral disposed in said motor chamber, said spiral havingone end fastened to said housing and the other end fastened to saidrotor shaft whereby said spiral causes said r-otor shaft to rotate inresponse to said spiral being heated;

a combustible material positioned in said motor chamber around saidspiral;

and means for selectively igniting said combustible material to causesaid rotor to rotate to an armed position with said aperture inalignment with said detonator and said booster charge.

References Cited BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner.

2. AN ARMING DEVICE COMPRISING: A HOUSING; A ROTOR MOUNTED FOR ROTATIONIN SAID HOUSING, SAID ROTOR HAVING AN ELONGATED SHAFT AND HAVING A ROTORDISC ON SAID SHAFT, SAID DISC HAVING AN AXIALLY EXTENDING APERTURETHERETHROUGH DISPOSED AT A PREDETERMINED RADIAL DISTANCE FROM THEROTATIONAL AXIS OF SAID ROTOR; A DETONATOR MOUNTED ON SAID HOUSING ONONE SIDE OF SAID ROTOR DISC; AN EXPOSIVE BOOSTER CHARGE MOUNTED ON SAIDHOUSING ON THE OPPOSITE SIDE OF SAID ROTOR DISC; SAID DETONATOR AND SAIDBOOSTER CHARGE BEING POSITIONED ALONG AN AXIS THAT IS PARALLEL TO SAIDROTATIONAL AXIS AND SPACED FROM SAID ROTATIONAL AXIS BY SAID RADIALDISTANCE SO THAT SAID ROTOR DISC ISOLATES SAID DETONATOR AND SAIDBOOSTER CHARGE WITH SAID ROTOR APERTURE SPACED FROM SAID DETONATOR ANDSAID BOOSTER CHARGE IN AN UNARMED POSITION OF SAID ROTOR; A MOTORCHAMBER POSITIONED IN SAID HOUSING AROUND SAID ROTOR SHAFT; A BIMETALLICSPIRAL DISPOSED IN SAID MOTOR CHAMBER, SAID SPIRAL HAVING ONE ENDFASTENED TO SAID HOUSING AND THE OTHER END FASTENED TO SAID ROTOR SHAFTWHEREBY SAID SPIRAL CAUSES SAID ROTOR SHAFT TO ROTATE IN RESPONSE TOSAID SPIRAL BEING HEATED; A COMBUSTIBLE MATERIAL POSITIONED IN SAIDMOTOR CHAMBER AROUND SAID SPIRAL; AND MEANS FOR SELECTIVELY IGNITINGSAID COMBUSTIBLE MATERIAL TO CAUSE SAID ROTOR TO ROTATE TO AN ARMEDPOSITION WITH SAID APERTURE IN ALIGNMENT WITH SAID DETONATOR AND SAIDBOOSTER CHARGE.